我为我的 android 项目创建了启动画面，如果我运行它，启动画面会出现一段时间并显示强制关闭消息，我应该怎么做才能导航到下一页？有什么建议么？
public class LoadingScreen extends Activity implements LoadingTaskFinishedListener {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Show the splash screen
setContentView(R.layout.activity_loading_screen);
// Find the progress bar
ProgressBar progressBar = (ProgressBar) findViewById(R.id.Progressbar);
// Start your loading
new LoadingTask(progressBar, null).execute("www.google.co.uk"); // Pass in whatever you need a url is just an example we don't use it in this tutorial
}
// This is the callback for when your async task has finished
public void onTaskFinished() {
completeSplash();
}
private void completeSplash(){
startApp();
finish(); // Don't forget to finish this Splash Activity so the user can't return to it!
}
private void startApp() {
Intent intent = new Intent(LoadingScreen.this, Rebuix.class);
startActivity(intent);
}
}
我的清单文件
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="15" />
<uses-permission android:name="android.permission.INTERNET" />
<application
android:icon="@drawable/rebuix"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".LoadingScreen"
android:label="@string/title_activity_loading_screen" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".Rebuix"
android:label="@string/title_activity_rebuix" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.rebuix.com.Rebuix" />
</activity>
<activity
android:name=".Login"
android:label="@string/title_activity_login" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.rebuix.com.Rebuix" />
</activity>
日志猫
11-23 13:13:03.798: I/Tutorial(459): Starting task with url: www.google.co.uk
11-23 13:13:14.156: D/AndroidRuntime(459): Shutting down VM
11-23 13:13:14.156: W/dalvikvm(459): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
11-23 13:13:14.166: E/AndroidRuntime(459): FATAL EXCEPTION: main
11-23 13:13:14.166: E/AndroidRuntime(459): java.lang.NullPointerException
11-23 13:13:14.166: E/AndroidRuntime(459): at com.rebuix.com.LoadingTask.onPostExecute(LoadingTask.java:68)
11-23 13:13:14.166: E/AndroidRuntime(459): at com.rebuix.com.LoadingTask.onPostExecute(LoadingTask.java:1)
11-23 13:13:14.166: E/AndroidRuntime(459): at android.os.AsyncTask.finish(AsyncTask.java:417)
11-23 13:13:14.166: E/AndroidRuntime(459): at android.os.AsyncTask.access$300(AsyncTask.java:127)
11-23 13:13:14.166: E/AndroidRuntime(459): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:429)
11-23 13:13:14.166: E/AndroidRuntime(459): at android.os.Handler.dispatchMessage(Handler.java:99)
11-23 13:13:14.166: E/AndroidRuntime(459): at android.os.Looper.loop(Looper.java:123)
11-23 13:13:14.166: E/AndroidRuntime(459): at android.app.ActivityThread.main(ActivityThread.java:4627)
11-23 13:13:14.166: E/AndroidRuntime(459): at java.lang.reflect.Method.invokeNative(Native Method)
11-23 13:13:14.166: E/AndroidRuntime(459): at java.lang.reflect.Method.invoke(Method.java:521)
11-23 13:13:14.166: E/AndroidRuntime(459): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
11-23 13:13:14.166: E/AndroidRuntime(459): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
11-23 13:13:14.166: E/AndroidRuntime(459): at dalvik.system.NativeStart.main(Native Method)
加载任务类
public class LoadingTask extends AsyncTask<String, Integer, Integer> {
public interface LoadingTaskFinishedListener {
void onTaskFinished(); // If you want to pass something back to the listener add a param to this method
}
// This is the progress bar you want to update while the task is in progress
private final ProgressBar progressBar;
// This is the listener that will be told when this task is finished
private final LoadingTaskFinishedListener finishedListener;
/**
* A Loading task that will load some resources that are necessary for the app to start
* @param progressBar - the progress bar you want to update while the task is in progress
* @param finishedListener - the listener that will be told when this task is finished
*/
public LoadingTask(ProgressBar progressBar, LoadingTaskFinishedListener finishedListener) {
this.progressBar = progressBar;
this.finishedListener = finishedListener;
}
@Override
protected Integer doInBackground(String... params) {
Log.i("Tutorial", "Starting task with url: "+params[0]);
if(resourcesDontAlreadyExist()){
downloadResources();
}
// Perhaps you want to return something to your post execute
return 1234;
}
private boolean resourcesDontAlreadyExist() {
// Here you would query your app's internal state to see if this download had been performed before
// Perhaps once checked save this in a shared preference for speed of access next time
return true; // returning true so we show the splash every time
}
private void downloadResources() {
// We are just imitating some process thats takes a bit of time (loading of resources / downloading)
int count = 10;
for (int i = 0; i < count; i++) {
// Update the progress bar after every step
int progress = (int) ((i / (float) count) * 100);
publishProgress(progress);
// Do some long loading things
try { Thread.sleep(1000); } catch (InterruptedException ignore) {}
}
}
@Override
protected void onProgressUpdate(Integer... values) {
super.onProgressUpdate(values);
progressBar.setProgress(values[0]); // This is ran on the UI thread so it is ok to update our progress bar ( a UI view ) here
}
@Override
protected void onPostExecute(Integer result) {
super.onPostExecute(result);
finishedListener.onTaskFinished(); // Tell whoever was listening we have finished
}
}